MACHINE NAVIGATION SYSTEM HAVING INTEGRITY CHECKING

• US 20120053831A1
• Filed: 08/25/2010
• Published: 03/01/2012
• Est. Priority Date: 08/25/2010
• Status: Active Grant

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: HALDER, Bibhrajit
• Granted Patent: US 8,700,324 B2
• Time in Patent Office: Days
• US Class Current: 701/439
• CPC Class Codes: G01C 21/165 combined with non-inertial navigation instruments
• CPC Class Codes: G01S 19/23 Testing, monitoring, correcting or calibrating of receiver elements
• CPC Class Codes: G01S 19/49 whereby the further system is an inertial position system, e.g. loosely-coupled

Abstract

A navigation system for a machine is disclosed. The navigation system may have a navigation unit configured to measure a position of a machine at a first time and at a second time, and at least a first sensor configured to generate at least a first signal indicative of a speed and a heading of the machine during a time period from the first time to the second time. The navigation system may also have a controller configured to estimate a position of the machine at the second time based on the measured position of the machine at the first time and the at least a first signal, and to make a comparison of the measured position of the machine at the second time with the estimated position of the machine at the second time. The controller may also be configured to determine an integrity of the navigation unit based on the comparison.

Claims

1. A navigation system, comprising:

a navigation unit configured to measure a position of a machine at a first time and at a second time;

at least a first sensor configured to generate at least a first signal indicative of a speed and a heading of the machine during a time period from the first time to the second time; and

a controller in communication with the navigation unit and the at least a first sensor, the controller being configured to;

estimate a position of the machine at the second time based on the measured position of the machine at the first time and the at least a first signal;

make a comparison of the measured position of the machine at the second time with the estimated position of the machine at the second time; and

determine an integrity of the navigation unit based on the comparison.

2. The navigation system of claim 1, wherein the at least a first sensor includes a speed sensor configured to generate a speed signal indicative of a travel speed of the machine, and a steering angle sensor configured to generate a first heading signal indicative of a heading of the machine.

3. The navigation system of claim 2, wherein the at least a first sensor further includes a pitch sensor configured to generate a second heading signal indicative of the heading of the machine.

4. The navigation system of claim 3, wherein the controller is configured to estimate the position of the machine at the second time based on signals from the speed sensor, the steering angle sensor, the pitch sensor, and known kinematics of the machine.

5. The navigation system of claim 1, wherein the navigation unit is a GPS unit.

6. The navigation system of claim 5, wherein the controller is configured to determine that the GPS unit has malfunctioned when the measured position at the second time is different than the estimated position at the second time by a threshold amount.

7. The navigation system of claim 6, wherein the controller is further configured to selectively implement evasive machine control when the GPS unit is determined to have malfunctioned.

8. The navigation system of claim 7, wherein the controller is further configured to selectively implement evasive machine control only when the GPS unit is determined to have malfunctioned for a set period of time.

9. The navigation system of claim 8, wherein implementing the evasive machine control includes at least one of changing a speed or a heading of the machine.

10. The navigation system of claim 9, wherein implementing the evasive machine control includes bringing the machine to a stop.

11. The navigation system of claim 8, wherein at least one of the threshold amount, the set period of time, and the evasive machine control are operator adjustable.

12. The navigation system of claim 8, wherein the controller is further configured to replace the measured position at the second time with the estimated position at the second time for machine control purposes when the GPS unit is determined to be malfunctioning.

13. The navigation system of claim 8, wherein the controller is further configured to make additional comparisons of estimated positions of the machine at successive instances in time with the measured position, and determine an accuracy of the GPS unit drifting based on trend analysis of the additional comparisons.

14. A computer readable medium for use by a navigation system, the computer readable medium having executable instructions for performing a method of accuracy checking a measured position, the method comprising:

measuring a position of a machine at a first time and at a second time;

measuring a speed and a heading of the machine during a time period from the first time to the second time; and

estimating a position of the machine at the second time based on the measured position of the machine at the first time and the measured speed and heading;

making a comparison of the measured position of the machine at the second time with the estimated position of the machine at the second time; and

determining an accuracy of the measured position of the machine at the second time based on the comparison.

15. The computer readable medium of claim 14, wherein measuring a heading includes measuring a steering angle of the machine.

16. The computer readable medium of claim 15, wherein measuring a heading further includes measuring a pitch of the machine.

17. The computer readable medium of claim 14, wherein determining the accuracy of the measured position includes determining that the measured position is inaccurate when the measured position of the machine at the second time is different than the estimated position of the machine at the second time by a threshold amount.

18. The computer readable medium of claim 17, wherein the method further includes selectively implementing evasive machine control when the measured position of the machine at the second time is determined to be inaccurate for a set period of time.

19. The computer readable medium of claim 18, wherein the method further includes replacing the measured position of the machine at the second time with the estimated position of the machine at the second time for machine control purposes when the measured position of the machine at the second time is determined to be inaccurate.

20. A machine, comprising:

a power source;

at least one traction device driven by the power source to propel the machine;

a GPS unit configured to measure a position of the machine at a first time and at a second time;

a speed sensor configured to generate a first signal indicative of a travel speed of the machine during a time period from the first time to the second time;

a steering sensor configured to generate a second signal indicative of a heading of the machine during the time period; and

a controller in communication with the GPS unit, the speed sensor, and the steering sensor, the controller being configured to;

estimate a position of the machine at the second time based on the measured position of the machine at the first time and the first and second signals;

make a comparison of the measured position of the machine at the second time with the estimated position of the machine at the second time;

determine that the GPS unit has malfunctioned when the measured position of the machine at the second time deviates from the estimated position of the machine at the second time by a threshold amount; and

implement evasive maneuvering of the machine when the GPS unit is determined to have malfunctioned for a set period of time.